This invention relates to detectors of ionizing radiation such as x-ray and gamma radiation. More specifically, the invention is concerned with improving multi-cell detectors which have various uses but are especially useful in computed tomography systems.
In the computed tomography process, a spatial distribution of x-ray photon intensities emerging from a body under examination is translated into electric signals which are processed in such manner that the image may be reconstructed and displayed. Background information on the process is given in an article by Gordon et al, "Image Reconstruction From Projections", Scientific American, October 1975, Vol. 233, No. 4. Detectors used in computed tomography must detect x-ray photons efficiently and with a high degree of spatial resolution. In some tomography systems, the x-ray source is pulsed and the pulse repetition rate can be limited by the recovery time of the x-ray detectors. It is desirable, therefore, to use x-ray detectors which have fast recovery time, high sensitivity, and fine spatial resolution. In some computed tomography systems, the x-ray beam has a fan shape and diverges as it exits from the examination subject whereupon the beam falls on an array of detector cells such that photon intensities over the leading front of the beam can be detected and resolved spatially. The individual detector cells are arranged in a stack or array so that x-ray photons distributed across the beam may be detected simultaneously.
In order to get good spatial resolution, it is desirable to have the electrode plates which comprise each cell spaced closely and uniformly over the entire length of the detector array. One prior attempt at achieving uniform and precise dimensions involves attaching alternate electrode plates to their connectors as one means of support and letting another portion of each of them bear on insulating supports. This method requires careful gauging of the distance between electrodes during assembly of the detector but there is still no assurance that the electrode plates will not be misaligned or distorted so as to upset the uniform distance between electrodes in the final assembly.